Any solution injected into tissues or into the circulatory system must be ____ to prevent cells from shrinking (crenation) or swelling.

Simple diffusion is the passive movement of molecules or ions across a semipermeable membrane from an area of higher concentration to an area of lower concentration, driven by the concentration gradient. In simple diffusion, molecules move randomly and spontaneously through the lipid bilayer of the membrane or through aqueous channels formed by integral membrane proteins. No energy input (ATP) is required for simple diffusion, as it occurs down the concentration gradient, from regions of high to low concentration, until equilibrium is reached. Simple diffusion is a fundamental process involved in the exchange of gases (e.g., oxygen, carbon dioxide) in the respiratory system, the absorption of nutrients and ions in the digestive system, the reabsorption of water and solutes in the kidneys, and the movement of signaling molecules across cell membranes. The rate of simple diffusion depends on factors such as the concentration gradient, temperature, molecular size, lipid solubility, and membrane surface area and permeability. Simple diffusion contrasts with facilitated diffusion, which involves the movement of molecules across membranes facilitated by transport proteins but still occurs down the concentration gradient without the expenditure of energy.

Cytokinesis is the final stage of cell division in which the cytoplasm and organelles are partitioned between two daughter cells, resulting in the formation of two new cells. In animal cells, cytokinesis involves the formation of a contractile ring composed of actin and myosin filaments at the equatorial plane of the cell, which contracts to create a cleavage furrow that pinches the cell membrane inward. This process eventually separates the parent cell into two distinct daughter cells, each containing a complete set of chromosomes and organelles. In plant cells, cytokinesis occurs differently due to the presence of a rigid cell wall. During telophase, the nuclear envelope reforms around the separated chromosomes, and the nucleoli reappear. Chromatin begins to decondense, and the spindle fibers disassemble. As telophase progresses, cytokinesis completes the cell division process, resulting in the formation of two genetically identical daughter cells. Telophase is preceded by anaphase, during which sister chromatids are pulled apart toward opposite poles of the cell by spindle fibers, and followed by cytokinesis, which completes the cell division process initiated during mitosis.

In DNA (deoxyribonucleic acid), nucleotides are composed of three components: a nitrogenous base, a deoxyribose sugar, and a phosphate group. The four nitrogenous bases found in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine forms hydrogen bonds with thymine, while guanine forms hydrogen bonds with cytosine. These complementary base pairs are held together by hydrogen bonds, with adenine pairing with thymine via two hydrogen bonds, and guanine pairing with cytosine via three hydrogen bonds. This base-pairing specificity is crucial for the accurate replication of DNA during cell division and ensures the fidelity of genetic information transmission from one generation to the next. The complementary base-pairing rule, also known as Chargaff's rule, states that the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine in a DNA molecule, maintaining a balance of purines (adenine and guanine) and pyrimidines (thymine and cytosine).

When a homozygous recessive individual (genotype: aa) is crossed with a homozygous dominant individual (genotype: AA) for a single trait, all offspring (F1 generation) will be heterozygous (genotype: Aa). In this case, all offspring will carry one dominant allele (A) and one recessive allele (a). The dominant allele will be expressed phenotypically in the presence of a single copy, resulting in a dominant phenotype. Since all offspring are heterozygous, 50% of the offspring will inherit the dominant phenotype, while the remaining 50% will inherit the recessive phenotype. This 1:1 phenotypic ratio is a characteristic of a monohybrid cross involving complete dominance.